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jBasics is a collection of useful utility classes for Java. This includes helper for XML, mathematic functions, restful web services helper, pattern oriented programming interfaces and more. Currently Java7 and up is supported. Version 1.0 will required at leaset Java8.
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/*
 * Copyright (c) 2009-2015
 * 	IT-Consulting Stephan Schloepke (http://www.schloepke.de/)
 * 	klemm software consulting Mirko Klemm (http://www.klemm-scs.com/)
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
package org.jbasics.arrays.unstable;

import org.jbasics.checker.ContractCheck;
import org.jbasics.checker.ContractViolationException;
import org.jbasics.types.sequences.Sequence;

import java.util.Iterator;
import java.util.ListIterator;
import java.util.NoSuchElementException;

/**
 * Simple {@link Iterator} to iterate over any typed array. While anything of this iterator is immutable the data
 * content given is NOT copied and can be changed by the caller. It is strongly recommended to only use the iterator
 * with constant arrays or copy them on construction.  An iterator cannot be thread safe and is also not immutable
 * because it requires to know the current position on the data. Therefore this iterator is neither thread safe nor is
 * it immutable. It should not be stored other than for the iteration moment within a single thread and needs to be
 * discarded right after. 
  A much better way to iterator over data with a guarantee to be thread safe and
 * immutable is to use the {@link Sequence} instead. 
 *
 * @param  The type of the data in the array.
 *
 * @author Stephan Schloepke
 * @since 1.0
 */
public class ArrayIterator implements ListIterator {
	private final T[] data;
	private final int offset;
	private final int size;
	private int next = 0;

	/**
	 * Create an iterator for the given data. The data is NOT copied therefore any change to the data will be reflected
	 * by the iterator as well!
	 *
	 * @param data The data to iterate over (MUST not be null).
	 *
	 * @throws ContractViolationException If data is null.
	 * @since 1.0
	 */
	public ArrayIterator(final T... data) {
		this.data = ContractCheck.mustNotBeNull(data, "data"); //$NON-NLS-1$
		this.size = data.length;
		this.offset = 0;
	}

	/**
	 * Create an iterator for the given data. The data is NOT copied therefore any change to the data will be reflected
	 * by the iterator as well!
	 *
	 * @param data The data to iterate over (MUST not be null).
	 *
	 * @throws ContractViolationException If data is null.
	 * @since 1.0
	 */
	public ArrayIterator(final int offset, final int size, final T[] data) {
		this.data = ContractCheck.mustNotBeNull(data, "data"); //$NON-NLS-1$
		this.size = ContractCheck.mustBeInRange(size, 0, this.data.length - offset, "size"); //$NON-NLS-1$
		this.offset = ContractCheck.mustBeInRange(offset, 0, data.length, "offset"); //$NON-NLS-1$
	}

	/**
	 * Create an iterator for the given data. The data is NOT copied therefore any change to the data will be reflected
	 * by the iterator as well!
	 *
	 * @param data The data to iterate over (MUST not be null).
	 *
	 * @throws ContractViolationException If data is null.
	 * @since 1.0
	 */
	public ArrayIterator(final int initialIndex, final T[] data) {
		this.data = ContractCheck.mustNotBeNull(data, "data"); //$NON-NLS-1$
		this.size = data.length;
		this.offset = 0;
		this.next = ContractCheck.mustBeInRange(initialIndex, 0, this.size, "initialIndex"); //$NON-NLS-1$
	}

	/**
	 * Create an iterator for the given data. The data is NOT copied therefore any change to the data will be reflected
	 * by the iterator as well!
	 *
	 * @param data The data to iterate over (MUST not be null).
	 *
	 * @throws ContractViolationException If data is null.
	 * @since 1.0
	 */
	public ArrayIterator(final int initialIndex, final int offset, final int size, final T[] data) {
		this.data = ContractCheck.mustNotBeNull(data, "data"); //$NON-NLS-1$
		this.size = ContractCheck.mustBeInRange(size, 0, this.data.length - offset, "size"); //$NON-NLS-1$
		this.offset = ContractCheck.mustBeInRange(offset, 0, data.length, "offset"); //$NON-NLS-1$
		this.next = ContractCheck.mustBeInRange(initialIndex, 0, this.size, "initialIndex"); //$NON-NLS-1$
	}

	/*
	 * (non-Javadoc)
	 * @see java.util.Iterator#hasNext()
	 */
	@Override
	public boolean hasNext() {
		return this.next < this.size;
	}

	/*
	 * (non-Javadoc)
	 * @see java.util.Iterator#next()
	 */
	@Override
	public T next() {
		if (hasNext()) {
			return this.data[this.offset + this.next++];
		} else {
			throw new NoSuchElementException();
		}
	}

	/*
	 * (non-Javadoc)
	 * @see java.util.ListIterator#hasPrevious()
	 */
	@Override
	public boolean hasPrevious() {
		return this.next >= 0;
	}

	/*
	 * (non-Javadoc)
	 * @see java.util.ListIterator#previous()
	 */
	@Override
	public T previous() {
		if (hasPrevious()) {
			return this.data[this.offset + this.next--];
		} else {
			throw new NoSuchElementException();
		}
	}

	/*
	 * (non-Javadoc)
	 * @see java.util.ListIterator#nextIndex()
	 */
	@Override
	public int nextIndex() {
		return this.next;
	}

	/*
	 * (non-Javadoc)
	 * @see java.util.ListIterator#previousIndex()
	 */
	@Override
	public int previousIndex() {
		return this.next - 1;
	}

	/**
	 * Optional operation to remove is not supported by this {@link Iterator}.
	 *
	 * @see java.util.Iterator#remove()
	 */
	@Override
	public void remove() {
		throw new UnsupportedOperationException();
	}

	/**
	 * Optional operation to remove is not supported by this {@link Iterator}.
	 *
	 * @see java.util.ListIterator#set(java.lang.Object)
	 */
	@Override
	public void set(final T e) {
		throw new UnsupportedOperationException();
	}

	/**
	 * Optional operation to remove is not supported by this {@link Iterator}.
	 *
	 * @see java.util.ListIterator#add(java.lang.Object)
	 */
	@Override
	public void add(final T e) {
		throw new UnsupportedOperationException();
	}
}